A Novel Microfabricated Formaldehyde Gas Sensor with NiO Thin Film

This paper presents a novel microfabricated formaldehyde gas sensor with enhanced sensitivity and detection resolution capabilities. The device comprises a silica microstructure suspended at a small distance above a glass substrate. A sputtered NiO thin film is used as the formaldehyde sensing layer. The gas sensor incorporates Pt heating resistors integrated with a micro hotplate to provide a heating function and utilizes Au interdigitated electrodes. When formaldehyde is present in the atmosphere, it is adsorbed by the sensing layer and causes a change in the electrical conductivity of the NiO film. Therefore, the measured resistance between the interdigitated electrodes changes correspondingly. The application of a voltage to the Pt heaters causes the temperature of the micro hotplate to increase, which in turn enhances the sensitivity of the sensor. The nanometer scale grain size of the sputtered oxide thin film is conducive to improving the sensitivity of the gas sensor. The experimental results indicate that the developed device has a sensitivity of 10 ohm ppm^-1 at 300degC and a detection capability of less than 1.0ppm